Transmitting device



Patented Mar. 18, 1924.

UNITED STATES PATENT OFFICE.

RAYMOND R. HERRMANN, OF ST. PAUL, MINNESOTA, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TRANSMITTING DEVICE.

Application riled January 24, 1922. SerialNo. 531,322.

To all whom it may concern:

Be it known that I, RAYMOND R. HERR- MANN, a citizen of the United States, residing at St. Paul, in the county of Ramsey, State of Minnesota, have invented certain new and useful Improvements in Transmitting Devices, of which the following is a full, clear, concise, and exact description.

This invention relates to transmitting devices, and particularly to a transmitter for use in telephone circuits.

In telephone transmitters it is customary practice to employ a resistance varying material which in most cases consists of granu lated carbon. The construction of these transmitters is such that the electric current necessarily passes through the granulated material and under certain conditions trouble is experienced due to the burning of the carbon and to packing of the granules to such an extent as to impair the transmitting efficiency.

The object of the invention is to provide a transmitter in which the diiliculties due to packing and burning are eliminated.

In general the invention provides a transmitter in which sound waves impinging upon a vibrating diaphragm set up corresponding fluctuations in an electrical circuit without employing a resistance varying material.

In the embodiment disclosed there is provided a transmitter in which the fluctuating currents are due to changes in reluctance of a mass of magnetic material, these changes in reluctance corresponding to the vibrations of the transmitter diaphragm.

Referring to the drawings, Fig. 1 is a cross-sectional view of a device embodying the invention.

Fig. 2 is a cross-Sectional view of a modifled construction.

Fig. 3 shows schematically the circuit arrangement for the device of Fig. 1, and

Fig. 4 is a schematic view of the circuit of the device of Fig. 2.

In the device of Fig. 1, the core consists of a section of insulating tubing 5 which is filled with filings 6 of magnetic material, preferably silicon steel. A diaphragm 7 which is also'preferably of silicon steel has secured to its central portion an armature 8 which is of the same material. This armature is adapted to move freely within the tube 5 upon vibration of the diaphragm and to close one end of the tube. In order to provide clearance and at the same. time prevent the filings from working out, a washer 9 of material such as felt is provided as shown. On the opposite side of the device there is provided a similar diaphragm, armature 11 and washer 12. The diaphragms 7 and are secured at their peripheries to a tubular member 13 of magnetic material such as silicon steel. Encircling the insulating tube 5 are the operating coils 14 and 15. The operating coil 15 is connected to a source of current supply 16 and upon vibration of either the diaphragm 7 or 10 there results a change in the reluctance of the magnetic circuit due to movement of the filings, which in turn results in corresponding current fluctuations being induced in the line winding 1 1. Since current does not pass through the comminuted material, there is no danger from burning and a transmitter of this type therefore can be used under conditions requiring high power output. For the same reason packing of the material due to thermal effects is entirely eliminated.

In the modified construction shown in Fig. 2, a single coil 20 is employed. This coil encircles a core comprising an insulating tube 21 which is filled with magnetic comminuted material 22 such as silicon steel filings.

A cup shaped housing 23 of magnetic material is employed as shown to which is secured a diaphragm 24, having an armature 25 rigidly secured to its central portion. To prevent escape of the comminuted material a felt washer 26 is employed as shown. The energy is supplied from the battery 27 through a pair of impedance coils 28 which prevent fluctuating currents from passing through the battery. Condensers 2929 are also connected in the line circuit to prevent the direct current passing out on the line. In either structure it is obvious that either one or two diaphragms may be employed as is most desirable for the condition under which it is desired to use the transmitter.

What is claimed is:

1. In a transmitting device, a coil, a core therefor comprising a section of oomminuted magnetic material, a pair of diaphragms having their central portions in contact with the respective ends of said core, and a magmagnetic circuit therefor said magnetic circuit including a diaphragm and a core section adjacent said diaphragm composed of magnetic filings, whereby the reluctance of the magnetic circuit Varied upon movement of the diaphragm in response to sound waves to induce a variable E. M. F. in the coil.

In witness whereof, I hereunto subscribe my name this 19th day of January, A. D.

RAYMOND R. HERRM ANN. 

